This invention relates to a germicidal UV reactor for use in fluid purifiers and to an UV lamp for use in such a germicidal UV reactor.
In the commonly used fluid purifiers, there are germicidal UV reactors used to effect sterilization, disinfection. The possible variety of fluids is wide, covering water, tap water, wastewater, any other water based liquid mixtures, liquid foods and beverages, and also non-water based liquids such as, for example, edible oils. This fluid can also be gaseous, such as air, for example, in case of air conditioners.
The germicidal effect of the UV radiation is well known. Published U.S. patent application Ser. No. 2004/0232846 discloses an amalgam mercury low pressure UV lamp. In order to reach an optimum temperature during operation of the lamp, means are provided for influencing the temperature of the amalgam. Common UV lamps used in germicidal UV reactors are not immersed directly into the liquid to be treated and disinfected. The temperature of the flowing water or other liquid is usually too low to maintain the necessary operating temperature of the UV lamp. Therefore, the lamp is sheathed in an UV transparent cladding tube, which results in an air gap between its inner wall and the outer envelope of the UV lamp. The low thermal conductivity of air guarantees at steady operation of the UV lamp that the latter will not cool down below the optimum temperature range. In some cases, however, the air gap is quite narrow in order to provide sufficient UV density at the surface of the cladding tube. The narrow gap diminishes its thermal resistance and thus the cooling effect on the envelope of the UV lamp.
The ignition of the UV lamp requires some time, in the order of a minute, until the desired operational germicidal efficiency is reached. Usually, continuous lamp operation is suggested, e.g. in water disinfection reactors, due to the long warm up period of germicidal UV lamps. In case of non-continuous lamp operation, the UV lamp is switched on only when water starts flowing. The germicidal effect is significantly reduced at non-continuous operation due to the long warming up of standard fluorescent UV lamp. U.S. Pat. No. 6,707,246 discloses a low-pressure mercury vapor discharge lamp with a discharge vessel, which is provided with auxiliary amalgam. This lamp has an improved warm-up characteristic whereby the lamp has a relatively short run-up time during the starting period. However, an immediate effect right after switching on is not yet expectable. Furthermore, the lamp temperature can vary over a longer period, e.g. in use of an UV reactor when the temperature of the flowing fluid changes.
Thus there is a particular need for an UV reactor for use in fluid purifiers and an appropriate UV lamp for the reactor in which the maximum germicidal efficiency is steadily provided both in quasi-immediate manner after switching on and during a long time use under changing external thermal conditions.